Process for coloring polyesters with rhodamine xanthene or benzophenyl safranine dyes

ABSTRACT

A process for mass-coloring polyesters characterized that there is admixed with the bis(hydroxyalkyl) aromatic dicarboxylic acid ester before carrying out a polyesterification or condensation, one or more ionic-polycyclic-heterocyclic dyestuffs selected from the group of substituted xanthylium and 5-6 mono- and 1-2, 5-6 dibenzophenazinium sodium and ammonium salts during the polymerization. Polyethylene terephthalate can be colored in this way and formed into colored films and filaments.

EJiie its tent Valiaveedan SAFRANINE DYES [72] Inventor: George DevasiaValiaveedan, Freehold Township, NJ.

[73] Assignee: E. I. du Pont de Nemours and Company,

Wilmington, Del.

[22] Filed: Apr. 21, 1969 [21] Appl. No.: 818,139

[52] US. Cl. .260/40 R [51] Int. Cl

[58] Field of Search ..260/40 [56] References Cited UNITED STATESPATENTS 3,359,230 12/1967 Bowman et a1. ..260/40 Feb.22,1972

Cooper et al. ..260/40 Bowman et a1.

Primary Examiner-Morris Liebman Assistant Examiner-L. T. JacobsAttorney-Lynn Barratt Morris {57] ABSTRACT A process for mass-coloringpolyesters characterized that there is admixed with thebis(hydroxyalkyl) aromatic dicarboxylic acid ester before carrying out apolyesterification or 6 Claims, N0 Drawings PROCESS FOR COLORINGPOLYESTERS WITH RHODAMINE, XANTHENE OR BENZOPHENYL SAFRANINE DYESCROSS-REFERENCE TO RELATED APPLICATIONS This invention is relates toAssignees pending application, .lohnes et al., Ser. No. 640,827, filedMay 24, 1967, now abandoned, covering the use ofN,N-diphenyldiamino-anthraquinone dyes for coloring shaped polyesterarticles.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionpertains to coloring film-forming polyesters with certain multiple ringdyestuffs to produce tinted polyester films, e.g., polyethyleneterephthalate films and other shaped articles.

2. Description of the Prior Art Various methods for the coloring ofhydrophobic organic polymers are known and have been applied in thoseindustries producing organic polymer films and fibers. In general, thecoloring processes for polymeric materials essentially involvedispersing or dissolving a pigment or dye therein in the polymer or byadsorption to a polymeric article. Such processes are disclosed inAssignees Pascal, U.S. Pat. Nos. 3,098,691 and 3,107,968, whereinacid-modified acrylic fibers are colored with water-insoluble multiplering dyes in dioxane and pyridine baths respectively. Although acidsystems are normally run at preferred temperatures between 80 and 105C., the coloring step may be shortened by raising the temperature to 200C. However, the elevated temperature may result in decomposition of thedye. In addition to the latter systems, R. Meek et al., U.S. Pat. No.3,278,468, discloses a process wherein the dye is incorporated in themonomeric material and becomes a part of the integral polymericstructure. In this instance, monomericpolyfunctional amines are causedto react with polyfunctional acid dye molecules or with polyfunctionalacids in the presence of a polyfunctional dye molecules capable ofreacting with either the amine or the acid to yield a colored polyamide.

Heretofore, particular-substituted anthraquinonic anthrapyridonic,anthrapyrimidine, isothiazolanthronic and phthaloylacridonic dyestuffssuch as those taught in Bowman et al., U.S. Pat. Nos. 3,413,257,3,424,708, and Assignees copending application Ser. No. 640,827,involved dyeing polyesters at high temperatures during polymerization.It is desirable that the dyestuffs be capable of withstanding hightemperatures up to 290 C., have a low volatility and to not sublime athigh temperatures and possess fastness to light, dry cleaning solvents,and photographic processing solutions.

It has been found that certain dyes of the rhodamine or Xanthene andbenzophenyl safranine classes are suitable for coloring syntheticpolyesters during polymerization and prior to the formation of shapedarticles.

In accordance with said copending application, Ser. No. 640,827disclosed, supra, and the prior art, wherein N,N'-diphenyldiaminoanthraquinone dyes are used to color linear polyesters,it has been found that the particular dyes that are described belowpossess the desired properties and have hightinctorial strength, andtheir use results in novel tinted or colored products of the invention.

SUMMARY OF THE INVENTION This invention relates to a process forimparting color to hydrophobic linear polyesters by addition ofparticular substitued xanthenes or rhodamines and benzophenyl safraninedyes to liquefied bis(hydroxyalkyl) aromatic dicarboxylic acid estersduring or after their preparation and prior to their condensation toform polyesters. The polyester may be the condensate resulting from 1)reaction ofa dicarboxylic acid, acid halide, or dialkyl ester with aglycol to form a bis(hydroxyalkyl)dicarboxylic acid ester by directesterification or catalyzed ester-interchange, and (2) subsequentpolyesterification. The dyes are present in the liquefiedbis(hydroxyalkyl)dicarboxylic acid ester or admixed therewith as thepolyesterification begins.

More precisely 0.015 to 1.0 gms of a 2,7-(N,N-dianilino) l0 orthobenzoate xanthylium salt, an 8,9-benzo-3,7-(N,N-dianilino) phenazine orcertain derivatives thereof are added per pound of his ester prior topolymerization at 280 to 305 C. Accordingly tinted shaped articles orphotographic film supports may be obtained therefrom upon extruding andbiaxially orienting the colored hydrophobic super polyester film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the preferredembodiments of this invention it is desired that apolycyclic-heterocyclic ionic dye such as benzophenazine, pyronine orxanthylium salt be added to the monomer of a linear polyester. Apreferred polyester may be the condensation, product of a monomericaromatic polycarboxylic acid, ester or anhydride and a polyhydricalcohol having two or more OH groups, HO(CH ),,OH wherein n is 2 to 10,e.g., that of a dimethyl terephthalate and ethylene glycol, as describedin Sorenson and Campbell, Preparative Methods of Polymer Chemistry,Interscience, New York, (1961) pp. 1 13. Preparation of said polyesterinvolves two ester exchange reactions under vacuum and nitrogen whereina small amount of a catalyst is used, e.g., metals, metal salts,mercuric or antimony oxides, calcium acetate dihydrate, zinc acetatedihydrate and various other catalysts containing alkaline and alkalineearth metals.

The monomer, preferably bis(2-hydroxyethyl) terephthalate, is formedupon addition of excess ethylene glycol to dimethyl terephthalate in areaction vessel equipped with a condenser, stirrer, and nitrogen purgesystem. Said vessel is immersed in an oil bath or suitable reservoircapable of sustaining the desired high temperatures for several hours.The catalyzed reaction system is heated to approximately 197 C. and thelast traces of the methanol released during polycondensation are removedby distillation as the nitrogen flow and vacuum pressure are reduced. Atthis point, there may be admixed with the bis(2-hydroxyethyl)terephthalate 0.015 g. or more per pound of monomer and one or morerhodamine dyes of the formula:

wherein R may be H, -CH or --C H R and R are H, or Chg, R is H, 50;, CHor COOH, and R is H or $0 In some instances, R and R may be identical orR is 50;, when R is H and R may be Na or H, unless ionization of thecarboxyl group, CO0", is indicated.

The resulting mixture is heated under a nitrogen atmosphere and excessethylene glycol is gradually distilled therefrom as the temperature isslowly increased to approximately 220-240 C. The supply of nitrogen isthen shut off and pressure is reduced to 0.3 mm. or less. Thepolymerization reaction is maintained under these conditions of vacuumfor 1 hour. The polymerization is continued at 285-290 C. for 3 hours.Stirring is adjusted to compensate for the change in viscosity. Uponcompletion of the reaction, the vacuum is slowly released, as the tintedpolymer is allowed to cool under a slow, steady stream of nitrogen gas.The yield of tinted polymer is quantitative, since no dimethylterephthalate is distilled in the early phases of polymerization.Accordingly, the resulting uniformly tinted polymer having a meltingpoint of about 254-255 C. was very viscous and possessed goodcold-drawing properties.

In place of the rhodamine dyes, there may be dispersed in the moltenpolyesterification system similar amounts of the substituted xanthenedyes of the formula:

O )2N :wamor- H" R2 l0 0 O O CzH wherein R may be CH or C H R is H or SONa when the ethylcarboxylate radical is replaced by a group and R is Hor CH;,. When the ethylcarboxylate radical above is replaced by S0 theClis not present. When numerically designating substitutions asindicated on page C35 of The Handbook of Chemistry and Physics, 49thEdition, Chemical Rubber Company, Ohio, 1968, a dye structure maycomprise two G-arnino, 7-methyl xanthenyl groups similar to that offormula II. In this instance, Q and M are hydrogen atoms.

The preferred dyes of the benzophenyl safraninc type essentiallycomprise hcterocyclically substituted phenazines which may or may nothave a benzo ring contiguously attached thereto between two adjacentcarbon atoms. Said dyes which have the desired properties and when usedin the above prescribed amounts are capable of tinting the bis(2-hydrox-35 yethyl)tercphthalate during the polyesterification have the followinggeneral formula:

wherein R may be a phenyl group, or an anilino group having an N-methylor ethylsubstituted radical in para position, and the groups may containfurther substituents, e.g., S0 SO Na and -CH;,. R is a CH;, or C Hgroup. Such dye structures are of the type illustrated on pages3417-3418 of the Color Index, Second Edition, Volume 3.

Mixtures of one, two, or more of dyes of formulas I and/or II and/or [IIcan be used for obtaining the tinted or colored polyester products, andthe products can be converted to films, plates, filaments, or fibers,etc. The dyes can be added conveniently from solution in ethyleneglycol.

There can be used according to the invention the dyes in the foregoingTable, and the dibenzophenyl safranines on page 3419 of the samereference: 50370 Acid Dyes and 50375 C. I. Basic Red 6.

When used to tint photographic film supports, the abovementioned dyesoffer a unique advantage in that they are leach resistant and the colorsthereof will not degrade. During high temperature (-300 C.)condensation, said dyes are uniformly dispersed and become integralparts of the tinted articles, films, etc., produced therefrom.

In accordance with this invention, it is required that dyes be solublein the molten polyester and stable at 290300 C. for several hours,resistant to sublimation under high vacuum of 1 mm. of mercury or lessunder polymerization conditions and possess appreciable tinctorialstrength at a concentration of 0.015 gms. or more per pound of monomer.In addition, said dyes must not have absorption peaks which would hinderthe photographic effect. Also, the dispersed dyes must remain fast andresistant to solutions throughout the shaped article, such asphotographic films, and not be leached therefrom during processing.Particularly useful for the process described herein are certainrhodamine or substituted xanthylenium salts and substituted mono anddibenzophenazines produced by the conventional methods disclosed onpages 3385-7 and 3417l9 of the Color Index, Second Edition, The AmericanAssociation of Textile Chemists and Colorists, Lowell, Mass, 1957.

The preferred class of xanthyliurn salts or amino-derivative (fluorinecoloring matter), are identified on page 3385 of the Color Index, (seeabove),

Any of the preferred dyes may be employed separately or in combination.Also said preferred dyes may serve in admixture with additional dyes orpigments normally not applicable to the molten-coloring processdisclosed herein. Coloring substances rendered useful upon admixing thesame with a preferred dye are the phthalocyanines, particularly copperphthalocyanine such as Monastral Blue. Said deep blue pigment isexceedingly stable at high temperatures and vacuum conditions forlimited periods. However, when incorporated into the polyester meltsystem such as that embodying this invention, said Monastral Blueyielded a greenish-blue tint instead of the desired blue color.Accordingly the preferred dyes are capable of intensifying the hueleaching out of any addi tional coloring substance which may sublime orincur color degradation.

The following examples illustrate the production of polyesters tintedwith a preferred dye or combination thereof but are not intended tolimit the invention as such.

EXAMPLE I Apparatus for coloring approximately 1 pound of monomer of thepreferred linear polyester, polyethylene terephthalate, duringpolymerization was assembled. A three neck-flask similar to a resinkettle was partially immersed in a silicone bath. In this instance, 450gms. of bis(2-hydroxyethyl)terephthalate, 0.0114 gms. isopropyltitanateand 0.03 gms. of zinc acetate were added to the reaction vessel. To saidvessel, there was added 0.1 g. of Pontacyl Fast Violet VR (Acid Violet9, C. I. 45,190) having the following structural formula:

in z 100 mls. of ethylene glycol.

The center neck was provided with a stainless steel stirrer having anair driven motor. A nitrogen rotameter purge system was connnected toone neck. To the third neck there was attached a condenser with a glycolreceiver flask.

A slow steady stream of nitrogen was introduced to the agitated mixtureand glycol distilled therefrom, as the vessel was gradually heated toabout 230 C. The nitrogen purge was discontinued and a vacuum of 0.6 mm.was sustained for 2 hours and 7 minutes at 280 C. Stirrer adjustmentswere made to compensate for the rise of inherent viscosity.

Shortly thereafter, chips of the cooled tinted polymer were sandwichedbetween two, one-twentieth inch thick chrome ferroplates. Said plateshaving highly polished surfaces had been treated with a conventionalresin moulding release lubricant, i.e., silicone resin, and preheated to275 C. in an oven for l2 hours. The sandwichlike arrangement was thenplaced in a conventional preheated laboratory melt press, provided witha device for mounting the platens. The platens were preheated for lminute at 275 C. and drawn together under 15,000 pounds pressure for 1minute at 282 C. The hot film and plate assembly was immediately removedfrom the press and quenched in cold water prior to comparison of thesame to a commercial photographic film base and a film without dyeprepared under the similar conditions. The film without the dye had aslightly yellowish tint throughout. However, the film so obtained havingthe Pontacyl Fast Violet VR therein had a uniform violet colorequivalent to that of the commercial film and had excellent fastness tolight.

EXAMPLE ll TABLE I Process Vacuum Process temperapressure, time, ture,C. mm hrs. Color 1 Pontacyl wool blue BL... 2815 1. 5 2 Purple. 2Pontacyl wool blue GL... 280 1.7 1. 65 Do.

Sample colors were fast and there was no indication of dye sublimation.

EXAMPLE III A large quantity of polyethylene terephthalate tinted with apreferred dye was prepared for use as photographic film base asdescribed in assignees US. Pat. No. 2,905,707. A metallic salt of a weakacid anion served as a suitable catalyst as the dyestuff was admixedwith the monomer, bis-(Z-hydroxyethyl) terephthalate in the esterexchange vessel. Although the dyes may be added directly to the reactionvessel, they are normally made into a slurry, prior to addition to themonomer, to facilitate dispersion. in this instance a slurry with of anethylene glycol solvent, having 2 parts of a magenta, and 1 part of ablue dye in combination with an aqueous carbon black dispersioncomprised the following:

A 45% aqueous carbon black solution produced by Colum ian Carbon Companyof New York.

The red and blue dyes were ball-milled separately in an appropriatequantity of ethylene glycol by conventional methods prior to admixing inthe slurry. The Aqua Blalt solution was added last to the bulk glycol inthe slurry container to avoid agglomeration.

ln a continuous process, the above-described slurry was introduced tothe bis(2-hydroxyethyl) terephthalate formed in the ester exchangevessel in a ratio of 1:486 parts by weight of finished blue tintedpolyethylene terephthalate. The heat softened polymer is extended 275 C.or more to a cooled-casting roll wherefrom the web is transferred andbiaxially stretched to desired dimensions after subcoating. The filmbase having a thickness of 0.004 inch was coated on each side with aresin substratum layer comprising vinylidene chloride,methylmethacrylate, itaconic acid, and ethyl acrylate as described inRawlins, Ser. No. 494,257 filed Oct. 8, i965. A gelatino silverbromoiodide photosensitive layer of 961:2 mgs./dm. was applied to oneside of the subcoated base. Said layer contained 2.5 percent of Agl and97.5 percent of AgBr and 170 gms. of gelatin per 0.282 gms. of silverhalide admixed with conventional emulsion ingredients such as the binderhardeners, surfactants, antifoggants, optical and chemical sensitizers,etc. ln this instance gelatin was the binder.

However, other natural or synthetic water permeable or water-solublecolloid binding agents would be suitable.

The photosensitive emulsion may be protected by an an tiabrasioncoating, e.g., of gelatin to which matting agents such as starch, SiOparticles, polymeric lattices, etc., may be added. The emulsion of thesample referred to herein is provided with a hardener which functions asa protective agent.

A sample film bearing the above-described negative emulsion and acontrol film-were simultaneously exposed for onefiftieth of a second ona Negative lBS sensitometer with a neutral density step wedge. Said stepwedge had 20 steps of variable densities decreasing by a factor of 2. Acommercial film bearing a similar emulsion layer was the control.Shortly thereafter the exposed films were developed in a conventionalmetol-hydroquinone developer for 6 minutes, fixed in a thiosulfatehardening bath for 10 minutes and immediately rinsed. The dry processedfilms were the compared.

it was observed the mixture of dyes, as described above and when usedaccording to this invention, have no adverse effect on the sensitometricproperties of the photographic emulsion nor on physical properties ofthe polyethylene terephthalate support.

EXAMPLE IV Using apparatus suitable for mass-coloring approximately 1pound of bis(2-hydroxyethyl) terephthalate during polyesterification bythe process and conditions described in Example I, as preferredsubstituted xanthene or rhodamine dye and a Monastral Blue pigment wereprepared. in this instance, mg. of Monastral Blue BWD or copperphthalocyanine having the formula:

and 250 mg. of Pontacyl Fast Violet VR (Acid Violet 9, C. l. 45,190)were admixed in a small amount of ethylene glycol prior to addition tothe reaction vessel containing 454 gm. of the above-mentioned monomer.

Accordingly the stable-tinted films of this invention may be used asphotographic film base, packaging materials, color filters or supportsfor other photosensitive materials such as photopolymerizable elementsand other graphic arts products, etc.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for imparting color to a hydrophobic, film formingpolyester characterized in that there is incorporated with abis(hydroxyalkyl) aromatic dicarboxylic acid ester before it isconverted to a polyester at an elevated temperature a small amount ofone or more of the dyes of the following formulas:

-COOR wherein R is H, -CH or --C H R and R each are H or CH R is H, SO-CH or COH, and R is H or 50;", R may be H or CH wherein R is -CH or CH,,; R is H or SO Na when the ethylcarboxylatc radical is replaced by anSO;," group and then a Cl'ion is not present, R may be H or CH andwherein R is phenyl or anilino group having an N-methyl or N- ethylradical in the para position, which groups can be further substitutedwith SO SO Na, or Cl-l radicals, and R is CH or C H 2. A processaccording to claim 1, wherein the dye is present during formation of thebisester.

3. A process according to claim 1, wherein the dye is added afterformation of the bisester and before the polyesterification is effected.

4. A process according to claim 1, wherein the polyester is polyethyleneterephthalate and the acid ester is bis(2-hydroxyethyl) terephthalate.

5. A process according to claim 1 containing only one dye.

6 A ydrophobic polyester film tinted or colored with one or more of thedyes defined in claim 1.

2. A process according to claim 1, wherein the dye is present during formation of the bis- ester.
 3. A process according to claim 1, wherein the dye is added after formation of the bis- ester and before the polyesterification is effected.
 4. A process according to claim 1, wherein the polyester is polyethylene terephthalate and the acid ester is bis(2-hydroxyethyl) terephthalate.
 5. A process according to claim 1 containing only one dye.
 6. A hydrophobic polyester film tinted or colored with one or more of the dyes defined in claim
 1. 